Is my 85hp producing enough power?

[TWPilot]

Update-
Changed the gaskets/diaphragm in the fuel pump.
Did the "shock treatment" of SeaFoam- lots of soot came out.

Took her out again this morning.
Did a couple things Jerry said to do:
Ran with the cover off. Nothing changed.
Adjusted the cam so that it fully deflected the carb plates- that actually lost 100 rpm (perhaps over-camm'd the carbs).
Didn't have anyone to go out with me, but listened to the motor at WOT, and it doesn't seem to be missing.

I think at this point, there's two possible outcomes:
1. Replace the reed plates and hope that was the issue.
2. This IS all the motor's got. It does immediately decrease in RPM if backed off from WOT, and does slow, so perhaps there really is nothing wrong with it, and it's all she's got. Just seems a bit slow for this small of a boat, with an 85hp motor on it...

 

[The Force power]

I suggest to get a "tiny Tach." to make sure of the RPMs otherwise it just guessing.
Verify the positions of the throttle-plates
Maybe drop down to a 15 P prop.
(although I have also a 85 hp. and it will rev. 5500+ with a 17 P on a 18' Bayliner with soaked foam lol)

36 MPH gps checked trimmed-out 37 MPH

 

[TWPilot]

*Update*

Ok- finally had a chance to go out on just a maintenance run with my daughter.

Airbox off.
Full-power, checked for "spitting" fuel out of the carbs- all three sucking as normal. No fuel coming back out. Would suggest reeds are good. Re-adjusted the cam so that the butterflies are horizontal while at full power.

Took a can of PowerTune with us. High idle, sprayed into each carb. Full-power, sprayed into each carb. Anchored and trimmed motor out of water. Pulled plugs, and sprayed directly into each cylinder while at TDC. Waited 15 mins/per. Cleaned plugs and ran motor again- full power. Lots of white smoke. Continued to spray into each carb while at full power.

Motor seems to be a bit smoother, and it gained 100rpm. Took her back home and did another compression check. Still the same at about 100psi in all three. Looks like I'm going to be replacing rings this winter... Not sure what else it could be...

 

[The Force power]

I would verify the readings with a different gauge & replace the head-gasket first, before tearing into the block

 

[TWPilot]

Only reason I'm not hitting directly on the head gasket- is that they all read the same. 100psi on the nose for all three. A head gasket would normally blow in one cylinder, and not all three- unless it was the middle and it blew into the other two...

Pulled the carbs- clean bowls, and the only abnormality was the top carb. The float went just past horizontal when upside down. Perhaps one cyl was putting a bit too much gas in it? That plug didn't look wetter than the rest when I pulled them... I thought I read somewhere that when the carbs are upside-down, the floats should sit horizontal...

All reeds are clean and complete- and look like they are closed completely.

Will put her back together and see if that changed anything. At this point, it looks like we're only talking about 7mph- and 700rpm... Will also do the link-n-sync again just to be sure.

 

[emoney]

So I didn't see where there was resolution on the controls. Are you sure the controls are in the correct notch and it's capable of advancing throttle all the way? I ask that question, because I had a Merc and replaced the cables and put them on incorrectly and it robbed me of 500 RPM. I confirmed that was the issue by forcing the throttle forward and then confirming there was still throttle left to use under the cowling. Just a thought.

 

[TWPilot]

So I didn't see where there was resolution on the controls. Are you sure the controls are in the correct notch and it's capable of advancing throttle all the way? I ask that question, because I had a Merc and replaced the cables and put them on incorrectly and it robbed me of 500 RPM. I confirmed that was the issue by forcing the throttle forward and then confirming there was still throttle left to use under the cowling. Just a thought.

If I just advance the throttle all the way forward- it stops around 4k. If I push down on the throttle, it gets an extra 200rpm. If I take my hand off, it backs down to 4k.

 

[The Force power]

Check if the shutters on the Carbs. are fully open in WOT setting, if not; adjust your cable either at the controls or at the Engine

 

[racerone]

You find a shop that has a test prop or a marine dynamometer.----This is a machine that test motor output.----Takes away the guessing !!

 

[emoney]

I think you may have a control cable issue. On my last boat w/90 hp Mercury it had side mount controls and when I replaced the cable, I didn't know it, but evidently there was an upper and lower pin location for the cable. I put it in the wrong one and it cost me about 500 rpm because the control was not advancing far enough. That's what people mean when they say "check to see if the shutters on the carbs are open fully when the control is in the farthest setting it will go". You can have some hold it in place while you go back and check the motor. You should see where the cable end attaches to the throttle advance on the motor. If you can push it even farther forward while the other person is holding the control down, then you've found your problem.

 

[TWPilot]

I think you may have a control cable issue. On my last boat w/90 hp Mercury it had side mount controls and when I replaced the cable, I didn't know it, but evidently there was an upper and lower pin location for the cable. I put it in the wrong one and it cost me about 500 rpm because the control was not advancing far enough.

I didn't see a slot for an upper and lower location- is that on the motor side of the cable, or the control? I haven't cracked open the side control box. Unless one of the previous owners replaced the cables, I don't think they'd crack that open.

 

[emoney]

It was in the control box. Did you confirm the cable isn't advancing the throttle far enough?

 

[TWPilot]

The carbs are off right now- but I'll let you know this afternoon when I get them back on.

 

[TWPilot]

It was in the control box. Did you confirm the cable isn't advancing the throttle far enough?

Got the carbs back on- and it looks like there's about another 20 degrees of travel to go to horizontal. Cracked open the control box, and sure enough, the throttle cable was in the top position. I moved it to the bottom position, and threw the lever. It looks like that gave me about 5-10 degrees of extra travel.

Going to take it out on the lake soon. Will let you all know what happened when I get back.

 

[emoney]

Looking forward to hear that solved the problem!

 

[TWPilot]

Welp, it didn't solve the problem- at this point, I think this is all this motor has.

What DID change, though- is now there is a "range" to the throttle. Before, it either had to be at WOT, or it wouldn't get on plane. It would max out at 4000rpm- unless you pushed down on the throttle, then it would gain that extra 200rpm. Now, at full deflection, it goes to 4200rpm and stays there.

Perhaps I did add enough extra weight to matter. The factory used dimensional lumber for the stringers, I used plywood. The factory used a single layer of glass over the stringers, there's roughly 3 layers now. The factory had a very thin layer of glass on the top of the floor only- now, there's an 8oz layer underneath, and 1708 on top. The factory tank was 17gal, now it's 32gal- geometrically in the same spot as the original. I haven't weighed the boat- but perhaps this may be the reason.

The other reason I think that this is all this motor has- It starts right up, every time. It doesn't bog down. It doesn't die- ever... It idles fine, it gets on plane quickly, and it holds that 4200rpm. Speed was measured by GPS at 28mph, but the rpms are estimated (gauge is aftermarket, based off what it was doing before I replaced it). She runs like a top. Oh well, for the rest of the season- I'll just be happy with what I've got...

Thanks to all for all the advice and help.

 

[Redbarron%%]

My experience with my 90 is that one cylinder dropping out will result in that loss of RPM. I would check with an induction timing light on each plug wire to see if each flashes at WOT.

 

[The Force power]

Welp, it didn't solve the problem- at this point, I think this is all this motor has.

What DID change, though- is now there is a "range" to the throttle. Before, it either had to be at WOT, or it wouldn't get on plane. It would max out at 4000rpm- unless you pushed down on the throttle, then it would gain that extra 200rpm. Now, at full deflection, it goes to 4200rpm and stays there.

Perhaps I did add enough extra weight to matter. The factory used dimensional lumber for the stringers, I used plywood. The factory used a single layer of glass over the stringers, there's roughly 3 layers now. The factory had a very thin layer of glass on the top of the floor only- now, there's an 8oz layer underneath, and 1708 on top. The factory tank was 17gal, now it's 32gal- geometrically in the same spot as the original. I haven't weighed the boat- but perhaps this may be the reason.

The other reason I think that this is all this motor has- It starts right up, every time. It doesn't bog down. It doesn't die- ever... It idles fine, it gets on plane quickly, and it holds that 4200rpm. Speed was measured by GPS at 28mph, but the rpms are estimated (gauge is aftermarket, based off what it was doing before I replaced it). She runs like a top. Oh well, for the rest of the season- I'll just be happy with what I've got...

Thanks to all for all the advice and help.

ONE last effort to try;
Change the prop to a 15 P
your motor will be slugging @ 4200 RPM's

 

[TWPilot]

My experience with my 90 is that one cylinder dropping out will result in that loss of RPM. I would check with an induction timing light on each plug wire to see if each flashes at WOT.

Kinda had another revelation- I checked timing with the cable in the old position- was that actually WOT? With it in it's new position- I'll check timing again, and adjust if necessary. I'll also check the other plugs as well while I'm at it...

 

[TWPilot]

Sure enough, timing was about 3 degrees off. And good light from the other two cylinders. Will let you know tomorrow how she did...