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  1. #1

    Default Soft Seized 351?

    Hello all, new to this forum, thanks for having me. I recently got an 89 Supra Comp with a recently rebuilt 351 that Id call broken in at this point. I thought he a starter problem, but eliminated that and found the engine hard to turn. It never started all that well, but did/will start and runs fine with a jump from my truck. Kind of at a loss, pulled all the plugs, nothing unusual. Am I missing something? Any help appreciated.

  2. #2
    Join Date
    May 2015

    Default Re: Soft Seized 351?

    How do you know you don't have a starter or electrical problem? If you can start it with a jump, I'd think you don't have a starter problem, but maybe a battery, cable or ground problem. If the engine struggles when cranking, it could be a timing problem. Too much advance will ignite early and try to push the piston down the wrong way. If the engine cranks easily with the jump, the problem is in the boat electrical system.
    Two common reasons for tight engines are bores-pistons-rings not properly sized or wrong bearings in a cheap overhaul. Owner assumes boars are worn oversize and buys over size rings, doesn't properly gap them and uses the old pistons. Same with the bearings, owner assumes crank is worn and buys oversize bearings or shims the existing bearings and now the clearance is too little. Unless you have receipts from a engine builder...
    I'm suspicious of boats sold with an overhauled engine that has some minor unresolved problem. Often the owner did a poor rebuild, can't figure out what's wrong so sells the boat with some story.

  3. #3
    Join Date
    Mar 2009
    Portland, Oregon,

    Default Re: Soft Seized 351?

    If you still have the old OEM starter motor....... it may not do the trick!
    I would suggest installing a HTGR/PMGR (high torque gear reduction/permanent magnet gear reduction) starter motor in lieu of the OEM non-gear reduction style starter motor!
    The HTGR/PMGR armature will turn approx 3 X's faster and will offer more torque to the pinion gear.

    Click image for larger version. 

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    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

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