1996 Voyager 320 - RPM & Planning Issues

[dkguimond]

Hi all,
New to the forum and will appreciate any help.
Purchased our Voyager several years ago and have always had issues with it getting up on plane.
Believe the engines are Cruisader 350 XL, 260 hp.
In 2020 blew the Starboard engine, reason was never determined (except it happened right after the carburator and timing was tuned by mechanic).

Decided to rebuild both engines because I didn't want an offset in the throttle. All went reasonably well, got up on plane for the 1st time ever - mechanic put in 750 double pumper Brawlers (vehicle carburetor). The issue became oil pouring out everywhere, rocker arms burning up and found out the wrong size rods had been used with small pieces of washers found under valve covers.

Found a new mechanic and rebuilt for the 2nd time. Engines run great but max RPM is 2900, should 4000 - 4400, as a result can't get up on plane.
Have tested all possible mechanical issues. Have pulled it out and bottom painted, put in rebuilt carburetors (Rochesters). Have spent more money than anyone even imagine.
Really love the boat but need to get to the bottom of the issue.
Props are 18 × 18, have been told by the prop guy to try 14 x 12, again more money spent without knowing if it will work.
Loaded boat weight is 18,000 lbs. Gear ratio is 1:1. WOT is 10 knots at 2900 rpm

Anyone have any other ideas, I'm at my witts end!

[km1125]

Of course smaller props will help you pop up on plane, but that is NOT the solution. And dropping to 14x12 would be a MASSIVE step down.

Knowing just what you wrote, you need to find out why the engines are not developing the power they should be.

Were the second engines built to the Crusader specs? Same type cam, rockers, etc? Same distributors? Same timing curves?

That does appear to be a pretty heavy boat for only 260HP engines, so if the second engine rebuild resulted less HP, that could be an issue.

[Cooler]

Prop size is not the issue. The prop guy simply did some math on effects of props, and wanted to sell you props. Still does not mean your engines are going to get to RPM. Limited RPM can be caused by various issues. Bad fuel, bad cables, bad job rebuilding, bad job reinstalling. I would go back to mechanic who rebuilt. He knows what he used for parts and how the job was done. Unfortunately, they always have a " but this, but that " explanation. The rebuilder was a certified marine mechanic, right? There is normally a guarantee of some sort. Hope things work out for you. Good luck. er

[bud37]

Welcome to the forum...

Quite the history there, this could simply be a tuning issue now......a couple ideas......if the distributors were never right as far as having the proper marine advance curves then the engines will not have ever made power at the right rpm and could have been the reason the other engine failed, also the carbs need to have the secondaries opening for the engines to make power.
What tells me this is your rpm vs speed, that speed is just pushing water and very close to getting over that wave. I would not run the boat like that until I got the tuning verified and corrected if the distributors turn out to be bad. Actually even one engine bad can hold them both back.

Honestly, IMO the props may not be the issue here unless they are damaged somehow, also do not run automotive carbs in marine engine compartments, they are not vented properly and can cause an explosion hazard. If you have the rochesters have your mechanic make sure the power circuit is working , secondaries opening......good luck man.

[Viper]

So first rebuilder didn't know what they were doing if they installed automotive carbs, who knows what else they screwed up on, automotive cams, distributors? Automotive carbs, while they are the base for marine carbs have no business being in a marine application, after the mods, they are not the same. Would have been important know what took the engine out the first time; wear, improper setting, wrong hardware, etc. There should have been internal signs/evidence of what caused the failure. It could have been something external to the engine that could cause the next engine to fail if left uncorrected, this is why it's crucial to determine the cause. Did the second rebuilder use the same components? Do you know if they dynoed the engines before installing them in the boat? Take a look at the casting (frost) plugs on both sides of the blocks, are they painted, silver, or brass? If they're painted, scratch some paint off of one and note the colour of the metal, they better be brass.

I'd go back to basics, do some simple tests like leak-downs, check vaccum, etc. and inspect the hardware; carbs, distributors, plugs, etc. A vacuum test can tell you a lot about how the engine is operating and whether some things are set properly or not. Then if everything checks out on the engines, the fault must be the boat side.

BTW, disconnect your tachs and sync gauge if applicable and see if you still have the same issue. It's easy to do and may eliminate one possibility.

[buster53]

OP, a lot of good thoughts and feedback from some very knowledgeable boaters especially the part about not putting an automotive carburetor in a boat…so what else did the mechanic do wrong?