new engine old pontoon boat is it prop ventilation

[HopeMcCloud]

old engine (Evinrude 70HP) finally died on 24' 1983 Sylvan two log pontoon which we refurbished ourselves 7 years ago. Best price was on Honda 60HP power thrust - installed where we bought it. Love the 4-stroke.

However: lots and lots of water splashing around and over motor/transom well. So much that we felt we needed to put the gas tank on the deck of the boat. Think we have a ventilation problem.

Do the hydrofoil and/or fins really work?

Should I go back to the dealer and discuss?

Prop is 9431-138-13 stainless steel. Brand new like the engine.

Should I post in props instead of pontoons? Or maybe both forums?

Thanks.

 

[ahicks]

Myself, I think the hydrofoils are a joke, especially on a pontoon boat.
Does all the water splash around wherever you have the tilt? Can you see where it's coming from? Like either side of the engine, or up through the center?

Did you/your dealer install the engine mounted all the way down with regards to the transom mounting holes?

Re: ventilation, are you able to run the engine at wide open throttle setting, or are you actually experiencing a ventilation problem causing the engine to over rev? If not actually ventilating, what rpm are you seeing?

Yours is the 3 cylinder engine, or 4? I have a similar prop on a Honda 90, 24' boat turning 6100rpm at about 25mph without issue.

 

[HopeMcCloud]

Does all the water splash around wherever you have the tilt? Worse when you raise the motor.

Can you see where it's coming from? Like either side of the engine, or up through the center? Blows up over both sides of the engine.

Did you/your dealer install the engine mounted all the way down with regards to the transom mounting holes? Yes it's lowered all the way down resting on top of the transom like the original Evinrude.

Re: ventilation, are you able to run the engine at wide open throttle setting, or are you actually experiencing a ventilation problem causing the engine to over rev? It revs up while getting up to speed then runs fine at full speed.

3-cyclinder.

 

[ondarvr]

It's not uncommon for toons to have some issues with ventilation at certain speeds, and the set up is critical, although sometimes it takes a while to get it right.

Pics will help.

​First ask the dealer about it, he may help you out.

​Foils can work at times to help prevent ventilation, but it's not the first option to try.

​After we see some pics you'll probably get some good advice.

 

[ahicks]

No telling for sure, because there's no such thing as a "universal" transom height, but I ended up with our 90 mounted 2 holes higher than the 89 40hp Johnson it replaced. No hint of ventilation or unusual splashing until I try taking off with the engine tilted out too far - which would be completely normal.

60 horse should be a sweetheart once you get it dialed in!

 

[Scott Danforth]

my guess the motor is installed too low. pontoons are the perfect candidate for a jack plate and PTT. as the weight increases, you need to raise the motor

fins are a joke

 

[ahicks]

Scott, his new engine is about the same weight as the old one, and comes standard with PTT.

The reason for the jack plate would be to make it easier to find ideal engine height (vs. experimenting using different mounting holes), or is there something I'm missing. No experience with them, and it seems like an expensive way to go is why I'm asking.

 

[Scott Danforth]

that is the reason that jack plates should be used. some old pontoons used to have an manual adjustable motor mount on a 4-bar linkage that worked great depending on what you had for weight on board. I do think those were limited to 30hp or so.

 

[HopeMcCloud]

We actually have tried two different heights. Initially installed two inches higher because dealer was did not want to cut into transom. We made the necessary modufication and lowered motor so it is now in same position as old motor . Seemed like the same amount of water splashing either way.

 

[HopeMcCloud]

Yes the motor weight is almost identical. One reason we went with the 60.

 

[ondarvr]

Are we going to see a pic

 

[HopeMcCloud]

Have to wait until we go out again to show the water. Will a dry picture on trailer be of any use?

 

[ondarvr]

Any pics you have will help, and both types are needed.

 

[HopeMcCloud]

No Title

 

[ahicks]

Engine height doesn't look too bad from what I can see. Picture is too small to do me much good regarding details though. When I blow it up to see what else might be going on, it looks like there might be a piece of angle material fastened to the bottom of the engine pod? If so, that needs to be removed or redone so it doesn't hang down so far. If you'd like, shoot me a PM and I'll give you my email so you can send a bigger version of that pic.

 

[ahicks]

Yup, maybe it's the pic, but something doesn't look right on the bottom of that engine pod. Something is sticking straight down from the bottom that's not supposed to be there. Maybe a mod they had to make to fit the engine that didn't get finished up? Dunno. Maybe another pic would show what's going on more clearly.

 

[ondarvr]

It's hard to tell from that pic, it gets too fuzzy when I zoom in, but.

​The motor looks low compared to the bottom of the pod, and high compared to the toons, so if that's the case, the water is hitting the lower unit and midsection higher than it should, but raising it may increase the chance of ventilation.

​Again, it's very difficult to make out details in the pic.

 

[HopeMcCloud]

No Title

I'll try posting a pic that is less compressed.

 

[ahicks]

OK, there you go. Clearly visible (now) is a plate of some sort sticking straight down from the bottom of the engine pod. It's visible just to the left of the bottom of the bottom roller (part of the trailer). Pretty sure that shouldn't be there....

There's a V cut in the center of it that makes it look to me like that plate USED to be horizontal, forming the bottom of the engine pod just ahead of the engine? My thought is that it was bent into the position it's in for clearance to mount the new engine as low as it is.

And the engine does look like it's mounted pretty low.

 

[clemsonfor]

Good eye. I see it too, I do beleive that was like the floor or bottom of the engine pod. It was flat to the bottom of the engine pod and extended out beyond the transom surface to the rear maybe an inch or 2 at most. ServerD as probably just a flat surface for pod to ride on. That honda looks to have a giant bracket that maybe someone bent it down? For the engine bracket to clear instead of cutting it flush with the transom? Just assumptions here and if we are both seeing it correctly, thanks to Ahicks sharp eye!!