Trojan Boat Forum

I have a 1980 F26 with a 305 MIE and a 14X11 prop. I’m getting 16-17 mph on my GPS at 2900 rpm., and that seems OK to me. But that’s all she wrote — won’t exceed 2900 rpm.

Here’s a flag: It has an HEI distributor with a vacuum advance, ported from the manifold. It appears to be “marinized” by sealing the vacuum pot at it’s entry point at the distributor. The motor idles very well (actually better if I detach and block off the vacuum advance), and I think I’m getting full mechanical advance by the 2900 rpm. The idle timing appears to be slightly advanced (about 12-15 degrees BTDC) with the vacuum advance plugged. At 2000 rpm without a load, the total advance appears to be somewhere around 30 degrees, but may be a little less.

I’ve read here that there is a filter and check valve coming off the tank, and I know the Rochester quadrajet carb I have has a filter in the front. (I haven’t tried to check it yet.) Would either of those filters, if blocked, cause only the top end problem? I have a great idle after warm up, no stalling, and get no hesitation with throttle up.

I’m arranged to have the compression checked, and have the timing confirmed. The throttle appears to fully open and the four barrel appears to operate (although I don’t get the noticeable power increase I’ve heard I should feel underway when the four barrel kicks in).

Are filters a likely issue, or insufficient mechanical advance? Maybe advancing timing under load at WOT to see if that does it? (think I could get the boatyard mechanic to go for a ride with me).

Open to thoughts and suggestions.

First you really should put a marine distributor in . Second All my listings on the F26 call for a 14x10 prop so that may be the issue . but I only list a 318 chry 225hp and a 351 233hp merc not the 305 .


Edit I found a listing for a 225hp merc ( not sure if its a gm or ford ) that calls for a 13x10 .

viewtopic.php?p=92919#p92919

Check out this post for some prop talk. I switched my old F27 (same boat as the F26) to a 14x10 and that thing would rip. 27 WOT.

I also had the 305 but it had the thunderbolt ignition system.

If you are seeing around 30 degrees advance at 2000, then that is about max, spec is probably closer to 27, unless you have engines with knock sensors etc. Maybe not such a good idea to advance timing past that point while under load as the timing curve is very important to avoid detonation. That said I agree with Mr Prowlersfish about getting a marine distributor as that one should have the appropriate curve in it, vacuum advance is completely useless in marine situations.
Maybe a prop change could let the engine spin up as others have said.

Appreciate the feedback. I had been running a 13X10 prop until this Spring. Top rpms were 3200-3300, and top speed was 12 mph. With the 13X10 I was hitting top speed at approx. 3000-3100 rpm. With the larger prop, I lost 300-400 rpm, but gained about 5 mph.

I’m waiting for the yard mechanic to come over and check both timing and compression for me. I checked the tach reading against a photo tach that I picked up, and the boat tach seems to be reading correctly.

I agree on the distributor — been looking around for a proper replacement, and will probably get that done over the winter or before launch in the spring. I’m aware of safety issues, and that’s sufficient reason to get the marine version. But I would also like to be confident the switch will get me a little better performance.

In the meantime, is there any feedback on filters? The motor runs smoothly throughout its range, so I’ve been thinking it’s probably not a fuel blockage issue — but sure have guessed wrong before.

If they put the right curve in that distributor chances are you won't see any difference. You can plot it with some timing tape, and at different rpms see what you get, the engine load will have no effect on timing advance ,it is strictly rpm related.I think if you do a search here on this, there is a thread about timing with some numbers that may help if it turns out you are having an issue.

There is 318 timing advance curve #'s buried in this forum??? The last missing Chrysler link to all my ignition woes. Could someone please post that curve and maybe Bob from beacon, could sticky that to the top of the home page. Oh wait a sec, he has a gm 305.