4 stroke 60/40 on 1648 River Rhino with UHMW??

[LarryMc]

You should check your impeller so that you will know for sure what you have. The aluminum 6 7/8 has the part number 10623 stamped on the lower end. The stainless has the part number 855708T60 cast on the inside of the upper end. Whoever converted the motor may have already swapped a stainless for the aluminum. You won't know until you look at it.

I have tested all three types of impeller in my motor trying to get the best performance. In my boat running in still water, the aluminum and stainless 2S impellers both run 4900-5000 RPM with 23-24 MPH. The cutback stainless 4S impeller runs 5100-5200 RPM and 25-26 MPH. The 2S impellers gave a little better holeshot but less max speed. As you can see, for practical purposes, there is not a lot of difference. At least, as far as my boat and motor are concerned.

Both the Stainless 2S & 4S impellers use the same part number, so you have to look at them to tell the difference.
The first photo below is the 4 stroke impeller alongside the 2 stroke impeller (4S on the left). The second photo is a closeup of the 4 stroke impeller

 

[LarryMc]

Now what I am wondering is if the 2 stroke pump is hindering my performance. It looks like the liner on the 4 stroke is much smaller, and the foot is smaller also.

There is no difference in the size of the intake for the AG & AGM pumps. The AG pumps used on the Mercury factory 2S jets used a bolt-in liner while the AGM use a flanged drop-in liner. That may be why they look different to you.

 

[stinkfoot]

Your link is broken, Larry. Rotus263, I would strongly advise you to call Brian at Outboard Jets. He is very helpful and knowledgeable even with obsolete old crap they don't make any more like I have. He went out of his way to help me even though there was little to no prospect of him selling me much more than a shift kit.

 

[LarryMc]

Got it!

 

[rotus623]

Wow Larry, thanks. It is great to have all your time and test data as a resource.

So I pulled the impeller tonight. First thing I did was take the grates out and measure impeller clearance. Last guy who put it on had it shifted to one side and I had close to .400 clearance on one end, and .300 on the other. I took the impeller out, sanded it up to clean up the castings, and dressed the leading edges. I could NOT for the life of me find any numbers on this thing at all, but from your pics, I can surely tell it is the 2s. Plus I know it is aluminum because of the color and the filings.

I ended up straightening out my grates, chiseling one side of each of them, and moving 2 shims up and setting my impeller clearance to .015 all around. I feel like this will make a difference for sure!!

At this point I think I should give her a run and if I'm still not satisfied maybe look for an4s impeller. What did that run ya Larry?

 

[stinkfoot]

So you didn't go with the SS one, Larry?

 

[LarryMc]

So you didn't go with the SS one, Larry?

Right now I am running the 2S stainless impeller that was in my old 2S motor. I'll probably go back to the 4S stainless that came with my new motor for the little extra speed, though. I'm also thinking about installing a set of Nauticus Smart Tabs to try improving the hole shot

rotus623: As you have already determined even though you didn't find a part number, the impeller in your motor is aluminum. The aluminum ones use a different key than the SS ones. The SS impellers use a square key. .

I didn't buy the 4S SS impeller, it came in my motor. Buying an impeller could be complicated since the part numbers (855708T60) are the same on both the 2S & 4S. The 2S in my photo was bought in June, 2014 from https://mercuryperformance.com/index.php for around $320 including shipping. But I don't know which type you would get now if you bought one using that part number. You can also find them on eBay for around $330. Jet Doctor has the same impeller for $410, probably close to $450 by the time you paid shipping. A dealer would likely charge you about the same as the Jet Dr, but at least you could look at before buying it and see which type you actually have.

 

[rotus623]

Cool man thanks! I think now that I have fixed my impeller clearance issue, dressed the impeller, straightened and cleaned up and chiseled the intake grates I will take her up the river alone and see how she rides. Certainly don't want to sacrifice what holeshot that I do have in this 4 stroke for a few MPH up top. I am going to bring two 80lb. bags of concrete and play with the weight (of another person) and see how it changes the dynamics of the boat. If that 160lbs. turns her into a slug, I think I will know what my next move is.............

 

[LarryMc]

Probably a good plan. Judging from my experience and the experiences of a few other posters on this site, I don't think changing impellers is going to help you all that much.

 

[rotus623]

Thanks a lot man!! Hopefully I can get her out for a few hours this friday and make some test runs.

 

[handyandy]

Lary if you decide to sell that 2s SS impeller I'll buy lol. Sorry I forgot to reply to you about the aluminum one you have. Any ways on the topic I think shimming will help you. Only thing I'd suggest when dressing the impeller I would sharpen the part that faces the ground when it's installed in the engine I always sharpen the what is the top side of the leading edges when it's installed. Seems like to me the impeller is able to get more bite in the water that way. As far as all the pump AG series pumps are all the same be it 2s or 4s they changed the shoes later on late 90's or early 2000's the drop in flanged liner type intake shoes. But the shoes can be interchanged on old and new pumps. I know because I have a older aluminum intake that uses a bolt in none flanged liner, and one of the rockproof UHMW intakes that uses a flanged drop in liner. They both work on my older AG 2s pump. The pump housing is the same. I got my pump used it had a long shaft drive shaft in it my motor is a short I just ordered a new drive shaft and swapped it. I could swap in a 4s long drive shaft and it would work on your 4s. Let us know how it does now once you get a chance to run it. I understand on the tunnel and the hull you run. For me my preference is a stout flat bottom currently I run a 15ft excel flat bottom it's heavy as well being a .125 thick hull all around no UHMW though on the bottom this is with a old 1993 2s merc up river just me fishing gear it can run 28-29, add a person it goes to 27-28, three guys and duck hunting gear so loaded down it does 25-27 takes a little while to get on step though. After goose season is out I have a 70hp evinrude 3cyl with a jet I'm going to swap to and add pods to the back.

 

[rotus623]

Lary if you decide to sell that 2s SS impeller I'll buy lol. Sorry I forgot to reply to you about the aluminum one you have. Any ways on the topic I think shimming will help you. Only thing I'd suggest when dressing the impeller I would sharpen the part that faces the ground when it's installed in the engine I always sharpen the what is the top side of the leading edges when it's installed. Seems like to me the impeller is able to get more bite in the water that way. As far as all the pump AG series pumps are all the same be it 2s or 4s they changed the shoes later on late 90's or early 2000's the drop in flanged liner type intake shoes. But the shoes can be interchanged on old and new pumps. I know because I have a older aluminum intake that uses a bolt in none flanged liner, and one of the rockproof UHMW intakes that uses a flanged drop in liner. They both work on my older AG 2s pump. The pump housing is the same. I got my pump used it had a long shaft drive shaft in it my motor is a short I just ordered a new drive shaft and swapped it. I could swap in a 4s long drive shaft and it would work on your 4s. Let us know how it does now once you get a chance to run it. I understand on the tunnel and the hull you run. For me my preference is a stout flat bottom currently I run a 15ft excel flat bottom it's heavy as well being a .125 thick hull all around no UHMW though on the bottom this is with a old 1993 2s merc up river just me fishing gear it can run 28-29, add a person it goes to 27-28, three guys and duck hunting gear so loaded down it does 25-27 takes a little while to get on step though. After goose season is out I have a 70hp evinrude 3cyl with a jet I'm going to swap to and add pods to the back.

Thanks a lot for the info on the AG pump, that makes me feel better. I didn't sharpen the other side of the impeller, but if I have to pull it again I surely will give it a shot.

I think a stout boat with no tunnel will give ya some better performance than the jet, for sure. Tunnel seems to suck the tail end down some. They say pods don't help while on plane, but I think if you put the right ones on they would work like trim tabs. I personally have rock ledges that I would like to get over top, and the lack of jet foot hanging down as well as UHMW covered chines will definitely help with that (hopefully). Lots of rock ledges in the James and the only way around some of em is up and over. Run in nose high and let her lever herself over :shock:

 

[handyandy]

where on the james do you fish I was in Fort lee for four months in 2014 over the spring and summer. Didn't have my jet on the boat then so ran it with a prop and jack plate as best I could got around pretty well for what it was. Floated it a number of times in my kayak I fished below the falls a lot for cat fish and above I put in all over the place from I think scottsville was the town on down.

 

[rotus623]

That's awesome Andy, those are the exact waters I Run. We fish out of scottsville, Columbia, maidens, howardsville etc. I also fish Watkins landing and ancarrows with the jet.

I also fish way down the James into Richmond for big blue catfish. Thats when I take the big boat out. For there and lake Anna stripers. Basically I am all over the map in his area depending on what time of year it is.

 

[handyandy]

I fished the apomatox river not sure on spelling near petersburg a lot when I was there since it was almost next door to the base. You couldn't really boat it I tried kayaking it a few times but in high water you got whit water, in low water those spots required dragging. There was a trail that followed the river most the way from petersburg up to the damn that formed some lake can't remember the name, but I'd ride my mountain bike with a milk crate I put on it with rod holder pipes up and down the trail to get to all the holes away from all the idiots of petersburg caught some good smallmouth in there. Pulled one just shy of 20" out from the apomatox. Had some good ones on the James. Caught quiet a few cats but never did get any monster blues biggest one was just shy of 20lbs if wasn't for that area being so urban, and having such weird water way laws on duck hunting the lower james I would try and move there. I'll have to be back at Fort lee for a month for some training possibly this spring summer, definitely next summer. When I go back there I will have my boat in tow, and will fish the upper james more smallies now that I have a jet. Will have to get in touch with you when I'm in that area.

 

[rotus623]

Yea bud gimme a shout for sure!! I put in at Hopewell a lot. That is right where the Appomattox comes into the James. I fish big stripers down that way in April-May.

 

[rotus623]

Ok guys did some test runs today. Brought 4 80lb bags of concrete to play around with weight. Took the two deep cycle batteries out of the bow.

With just me, trolling motor, start battery and 8 gallons of fuel she did good. Got on plane well (maybe 1.5 boat lengths) and ran 24.5 on the gps.

With 160lbs in the rear seat area she didn't seem to take any longer to get on plane, and mostly felt comfortable. Ran 23.5 per gps.

With 160lbs of dead weight in the bow(simulating trolling motor batteries and gear) and 160lbs in the rear seat area, she ran 22.5. Felt a little slower to plane. Handled the load pretty well but definitely sat a little lower in the water when running.

Still not sure how much water she drafts to plane but I think it is much less than I thought.Here is the issue I am having: when hitting waves there are no issues. When getting on plane she wants to cavitate if I gun it. If I ease it into wot it's not as bad. It also will cavitate when the water has lit chop and while turning hard. Do you guys think those "water wings" on the foot will get rid of this?

 

[LarryMc]

The fins will help a lot on a non-tunnel jet to reduce cavitation. I'm not sure about a tunnel boat, though. Given that a tunnel is designed to force water into the intake and the fins are also designed for the same thing, I kind of doubt it. I've had them on my boat a few times but they usually don't last long (at least for me) on a non-tunnel boat because they lower the amount of clearance that you have on the front edge of the intake. That wouldn't be a problem on a tunnel boat, though.
They will improve the steering on a jet if that matters to you. I know that the stern on flat bottom jets is bad to slide around on turns. My Lowe also slides quite a bit on turns and when I had the fins on, they helped to reduce the amount of sliding. I just got tired of replacing (and buying) them when they got beat up too bad to straighten out .

Send Brian O'Leary of Outboard Jets an email at [email protected] and ask him about the fins. He can give you more information about how they will work on a tunnel boat than I ever could. He usually sends a reply within a day or so and he's very good about helping people out with questions about their boats.

 

[rotus623]

Thanks I will surely do that. I also believe that my impeller is dull because that is one of the main reasons for cavitation on acceleration according
To outboard jets.

 

[rotus623]

So I had a little fun with my engine this weekend.

I pulled the spark plugs and put some fresh ones in, changed the oil, and adjusted the valve clearances. I sharpened the impeller a little bit more and took her for a spin.

I noticed that she got on plane a little easier without cavitation on take off. So that's a plus. I may want to experiment with a new impeller and possibly liner. I only have 2 washers to go on this one!!