3.0 Mercruiser on Plane

[cedarswamp]

I have a 3.0 Mercruiser in a 19' Starcraft superfisherman, Doesn't want to get on Plane and at Top speed only reaches 25MPH , I have done a complete tune up , to engine! I do have a Honda Kicker motor also mounted , so there is that added weight. Seems like this set up should run in low 30s anyway, Does anyone have any suggestions? 

[Bozeman Bob]

Did it get up on plane before the kicker ? What RPMs are you turning and what is the motor rated for ? Have you done a compression test ? Is the throttle cable pushing the carb wide open ? Verify the linkage by removing it at carb and manually moving carb linkage. How old is the boat and is the flotation waterlogged ? Check weight at scale house. You may be over propped if previous owner ran it light and you added a tone of equipment. Prop hub could be slipping as well. Is kicker in water and dragging when you open her up ? Has it been timed recently ?

[Steve.e]

May just need trim tabs. I put them on my 19' islander, made a world of difference. I also have a kicker. Starcrafts are generally bow light.They also make lower unit fins that attach pretty easily and will plane you just fine.

[cedarswamp]

Just bought this boat, and it ran rough when i purchased it, so before taking it out I did the tune up, a buddy also said the timing could be off a little! Boat is an Aluminum 93 Starcraft, 19' Superfisherman! Kicker is up when running with 3.0, I will check the linkage to carb. also

[cedarswamp]

I was considering a Fin ! How much do the trim tabs cost ? 

[Bozeman Bob]

You should not need a fin or trim tabs, adjust the trim on your outdrive to compensate for load. Trim tabs in your case is for balancing the boat left to right not bow to stern. A fin will create more drag and if they were all that great Mercruiser would be offering  them or selling aftermarket kits as well. Electronic ignition or points  ?

[cedarswamp]

Has Electronic ignition

[Bozeman Bob]

I wonder if the previous owner switched props to get better fuel mileage, which many people think will happen by doing that. They are wrong, best fuel rate will come from engine running a couple hundred under factory redline with full load. Yes that boat should run in the mid 30's. The waterlogged foam and possible weight associated with that would be the last thing I looked at after verifying all the engine specs. Does it have a remote fuel filter and if so have you changed it ? You could mark the distributor and when under way turn it slightly in either direction to see if it picks up speed,if not move it back to the etched mark. If it does then have your buddy or auto repair shop time it correctly.

[Bozeman Bob]

When I say best fuel rate I am referring to the engine running so its not lugging or over revving. Most of the time your best economy is around 3,000 rpm.

[cedarswamp]

Yes it does have a Remote filter, and i did change that ! I am gonna try the distributor turning it, see if its not timed properly! Thanks Bob

[cedarswamp]

Update, Timing was off quite a bit! Adjusted the distributor, and tweeked the carb! All sorts of power now! Rpms at full throttle 5000, before only 4100! Seems good to get on plane quick! Thanks for all the help. Paul

[L&M]

What you think is right adjusting it by the above method and what is good can be two different things. If you didn't set it correctly  with a light for that model distributer, weather it be after market electronic or especially the delco system you'll do more harm over the long run than good. Just sayin

[Bozeman Bob]

What you think is right adjusting it by the above method and what is good can be two different things. If you didn't set it correctly  with a light for that model distributer, weather it be after market electronic or especially the delco system you'll do more harm over the long run than good. Just sayin

Completely agree ^^^ Should of been clearer on my suggestion. Just wanted to see if the timing was the problem. Now that you see how it performs you must time it to spec or you may burn a piston with th timing possibly too far advanced. Also must check rpms vs what it is rated for by mfg, same bad result if your over revving it. Glad to hear that was it, now put timing light on it.

[Bozeman Bob]

Oh and I did write in a previous post if that was it too have a shop or your buddy time it correctly. [Just reread that post to make sure I did not give out info that may ruin your engine.]

[cedarswamp]

Ok, Yes I Looked it up yesterday and it did say max RPMs should be between 4400-4800 and it was slightly over 5000 at full , so yes we do need to use a timing light to get it dialed in. Last thing I want is to do harm to it.